target/riscv/pmp: Fix address matching, granularity and debug

- Add tracing to CSR reads and writes to pmpcfg and pmpaddr.
- Rename pmp_hart_has_priv to pmp_has_access.
- Simplify address matching rules and fix bug where positive
  matches could be missed.
- Mask addresses so that granularity can be detected and enforced.
- Add note regarding issue with entries whose length is less than
  or equal to the 2 ^ TARGET_PAGE_BITS granularity.
- Convert PMP debugging to trace-events and remove redundant
  debugging statements.

target/riscv/cpu_helper.c

@@ -465,7 +465,7 @@ int riscv_cpu_handle_mmu_fault(CPUState *cs, vaddr address, int size,
             "%s address=%" VADDR_PRIx " ret %d physical " TARGET_FMT_plx
              " prot %d\n", __func__, address, ret, pa, prot);
     if (riscv_feature(env, RISCV_FEATURE_PMP) &&
-        !pmp_hart_has_privs(env, pa, TARGET_PAGE_SIZE, 1 << rw)) {
+        !pmp_has_access(env, pa & TARGET_PAGE_MASK, rw)) {
         ret = TRANSLATE_FAIL;
     }
     if (ret == TRANSLATE_SUCCESS) {